I. Field of the Invention
The present invention pertains generally to the field of wireless communications, and more specifically to methods and apparatus for providing secure transmissions in a wireless communication system.
II. Background
A modern day communication system is required to support a variety of applications. One such communication system is a code division multiple access (CDMA) system that conforms to the “TIA/EIA/IS-95 Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,” hereinafter referred to as the IS-95 standard, or a CDMA system that conforms to the “TIA/EIA/IS-2000 Standard for cdma2000 Spread Spectrum Systems,” hereinafter referred to as the IS-2000 standard. Another CDMA standard is the W-CDMA standard, as embodied in 3rd Generation Partnership Project “3GPP”, Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214. A CDMA system allows for voice and data communications between users over a terrestrial link. The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS”, and U.S. Pat. No. 5,103,459, entitled “SYSTEM AND METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM”, both assigned to the assignee of the present invention and incorporated by reference herein. Other examples of communication systems are time division multiple access (TDMA) systems and frequency division multiple access (FDMA) systems.
In this specification, base station refers to the hardware with which the remote stations communicate. Cell refers to the hardware or the geographic coverage area, depending on the context in which the term is used. A sector is a partition of a cell. Because a sector of a CDMA system has the attributes of a cell, the teachings described in terms of cells are readily extended to sectors.
In a CDMA system, communications between users are conducted through one or more base stations. A first user on one remote station communicates to a second user on a second remote station by transmitting data on the reverse link to a base station. The base station receives the data and can route the data to another base station. The data is transmitted on the forward link of the same base station, or a second base station, to the second remote station. The forward link refers to transmission from the base station to a remote station and the reverse link refers to transmission from the remote station to a base station. In IS-95 and IS-2000 FDD mode systems, the forward link and the reverse link are allocated separate frequencies.
In the field of wireless communications, security of over-the-air transmissions has become an increasingly important aspect in communication systems. Security is often maintained through encryption protocols that prevent disclosure of private communications between parties and/or prevent rogue mobile stations from accessing services for which payment has not been rendered to the communication service provider. Encryption is a process whereby data is manipulated by a random process such that the data is made unintelligible by all but the intended recipient. Decryption is simply the process of recovering the original data. One type of encryption algorithm commonly used in the industry is the Enhanced Cellular Message Encryption Algorithm (ECMEA), which is a block cipher. Due to the sophistication of modem day code-breakers and “hackers,” a need presently exists to create stronger, more secure encryption processes to protect users of wireless communication services and service providers.